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2007 XT - 5MT ELH, EWG, E85, Kinugawa TD06SL 20G 8cm
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1,587 Posts
Discussion Starter #1
Prior to getting tuned for the 18G build will be replacing spark plugs (still running stock at 72,000 miles). Planning to run 20 PSI tune (325 wtq is the goal). Not sure if go with 1-step colder or stock range, searched but so far I haven't found conclusive data.
 

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Premium Member
2009 Outback XT-B 5MT
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10,254 Posts
Almost no one needs colder plugs. Stock plugs work great to well above 600whp.
 

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8,844 Posts
IF you're going to be beating on it and driving it at full boost and WOT -all- the time, then you might be able to use them. However if you drive at all off boost or daily drive, the one step colder plugs will just foul quicker. I'd stick with stock heat range unless you're having a problem with preignition. Theres a good unabomber thread on nasioc about spark plugs : http://forums.nasioc.com/forums/showthread.php?t=518633

Almost no one actually needs 1 step colder plugs.
 

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Administrator
2007 Forester Sports XT 4EAT
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39,810 Posts
I had a COBB dyno protune done at COBB Tuning Surgeline & the tuners, Tim Bailey & Lance Lucas, recommended an upgraded fuel pump & one step colder spark plugs. I had the time to install the Walbro fuel pump, but I still need to install the NGK Iridium LFR7AIX (2309) spark plugs. My COBB dyno Protune write up can viewed here. :smile:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]
 

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2007 XT - 5MT ELH, EWG, E85, Kinugawa TD06SL 20G 8cm
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1,587 Posts
Discussion Starter #6 (Edited)
Oh, well still the same story, some say YES some say NO, so decided to go with stockers (free with Subaru bucks) since this is a daily driver following funkeymonkeys advice (...the one step colder plugs will just foul quicker. I'd stick with stock heat range unless you're having a problem with preignition)...

Will see if the tuner likes the stockers (Scott Siegel @ Forged Performance).
 

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2006 Forester XTI LTD SG9 2007 STI 6 speed, HP Techs-MPS SSLR 2.5, Junior Tuned, 573 WHP/ 500 WTQ
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554 Posts
I am running 1 step colder per my tuner's recommendation and all seems fine. The car is running very smooth pulling hard and i saw an increase in gas mileage to boot. I had been consistently seeing 22-24 mpg at 70-80 mph highway speeds (and the 5 speed) with my current plugs and tune. I hope to see better with the 6 speed.

Don't say it Dave:) I know what your thinking!
 
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